Method of dyeing polymers containing nitrile groups and articles made of same

ABSTRACT

A method of dyeing polymers containing nitrile groups and articles made from such polymers so as to impart colors thereto ranging from yellow to brown, according to which sulfur is introduced into said polymers and articles made therefrom by treating them with an aqueous solution of hydrosulfuric acid or salts thereof in a neutral medium with a subsequent treatment of said polymers and articles in a weakly acidic medium. Further treatment with a metal salt capable of forming a chelate with the sulfhydryl groups in the dyed polymer imparts decay-resistance, light-fastness, thermal stability and hydrophobic properties.

United States Patent [191 Makhkamov et al.

11] 3,790,341 Feb. 5, 1974 METHOD OF DYEING POLYMERS CONTAINING NITRILE GROUPS AND ARTICLES MADE OF SAME 22 Filed: Jan. 12,1970

211 Appl.No.:2,353

[52] US. Cl 8/52, 8/21 A, 8/171,

81/128 R, 26( )/778, 260/79.3 R, 260/V79.5 R, 260/17.4 51 Int. Cl. D06p 1/00, D06p 3/82 [58] Field of Search. 8/21 A, 52, 171, 128; 260/778 [56] References Cited UNITED STATES PATENTS 2,563,640 8/1964 Brown 260/79.5

8/1951 Rothrock ..260/79.5 9/1940 Schlack 8/29 Primary Examiner-George F. Lesmes Assistant Examiner-Patricia C. Ives Attorney, Agent, or Firm-Waters, Roditi, Schwartz and Nissen ABSTRACT A method of dyeing polymers containing nitrile groups and articles made from such polymers so as to impart colors thereto ranging from yellow to brown, according to which sulfur is introduced into said polymers and articles made therefrom by treating them with an 7 aqueous solution of hydrosulfuric acid or salts thereof in a neutral medium with a subsequent treatmentof said polymers and articles in a weakly acidic medium. Further treatment with a metal salt capable of forming a chelate with the sulfhydryl groups in the dyed polymer imparts decay-resistance, light-fastness, thermal stability and hydrophobic properties.

12 Claims, No Drawings METHOD OF DYEIN G POLYMERS CONTAINING NITRILE GROUPS AND ARTICLES MADE OF SAME The present invention relates to the textile industry and more particularly to a method of dyeing polymers containing nitrile groups and articles made of such polymers.

Polymers containing nitrile groups are widely used for producing synthetic fibres, plastics and other products.

The term polymers containing nitrile groups is used to denote polyacrylonitrile and its derivatives, cyanoethylated derivatives of cellulose and polyvinyl alcohol, graft copolymers of cellulose, polyvinyl alcohol or polyamides with polyacrylonitrile. Said polymers or their mixtures with other polymers can be used for manufacturing various products.

Various methods are known of dyeing polymers that contain nitrile groups, by using different dyes, so that the resulting colors range from yellow to brown. Not all dyes, however, exhibit adequate fastness. Most fast colors are obtained when dyeing cyanoethylated cellulose or graft copolymers of cellulose and polyacrylonitrile with cationic or vat dyes. Cationic and vat dyes are quite costly and, besides, dyeing with the use of vat dyes is a complicated and lengthy process.

An object of the present invention is to provide a method of dyeing polymers containing nitrile groups with the resultant colors ranging from yellow to brown, which will ensure high stability of the colors, the. dyein g process being simple and economically expedient as to its cost.

Another object of the present invention is to provide such a dyeing process, after which polymers containing nitrile groups will be not only colored, but will also feature an improved stability to solar and ultraviolet radiation, to the action of microorganisms, and have hydrophobic properties.

The essence of the method of the present invention resides in that sulfur is introduced into polymers containing nitrile groups or into articles made of such polymers, by treating them with an aqueous solution of hydrosulfuric acid or its salts in a neutral medium with a subsequent treatment in a weakly acidic medium.

As hydrosulfuric use should-be made of sulfides of alkali metals or of ammonium sulfide. Sodium sulfide is preferable among sulfides of alkali metals.

Said polymers or articles made therefrom are treated with aqueous solutions of hydrosulfuric acid or its salts whose concentration should be not lower than 3 wt. percent. The concentration of aqueous solutions of hydrosulfuric acid or its salts is so'selected, that, taking into account the content of nitrile groups in the polymers or in articles made therefrom, the content of sulfur in the polymers should be not less than 2.5 wt. percent for coloring them from yellow to orange, and not less than 8 wt. percent for the resulting colors to be from orange to brown. It is possible to obtain intermediate tones: yellow, golden-yellow, orange, red-brown, brown and dark brown.

A neutral medium with a pH 7-7.5 when treating said polymers or articles made therefrom is maintained by introducing a required amount of a phosphate buffer; it 'is preferable to use monobasic potassium phosphate for such a buffer.

After treating polymers or articles made therefrom with aqueous solutions of hydrosulfuric acid or its salts, the polymers or articles are placed into a weakly acidic medium whose pH is maintained within 4-6. Said pH value is maintained by introducing a mineral acid, preferably sulfuric acid, using its 3 percent aqueous solution.

For imparting new properties to said polymers and articles made therefrom, namely, for making them decay-resistant, water-resistant and bactericidal, the polymers and articles produced from them, after sulfur has been introduced into them, that is, after they have been treated with aqueous solutions of hydrosulfuric acid or its salts and then in aweakly acidic meidum, are treated with aqueous solutions of salts of certain metals capable of forming a chelate compound with sulfhydryl groups. Salts of copper and nickel may be cited as an example. The formation of a chelate compound is accompanied by a change in the shade of the color of the material.

The present method of dyeing polymers containing nitrile groups, as well as articles made therefrom may be carried out either in a periodic-cycle, or in a semicontinuous cycle.

In the first case the treatment with said sulfurcontaining compounds is effected by heating to a temperature in the range of -l00 C, preferably from to C, for 30-360 min., preferably for 60 min. In the second case, that is, when the process is run according to a semi-continuous cycle, the treatment is carried out under the same temperature conditions, but for 05-10 min., preferably for 3-5 min., with a subsequent removal of excess impregnating solution and with steaming at a temperature of l0O-l05 C for 1-20 min., preferably for 10 min.

When effecting the present method of dyeing in a periodic fashion, the introduction of sulfur into said polymer or into articles made therefrom is carried out by immersing them into an aqueous solution of hydrosulfuric acid or its salts with the pH 7-7.5 maintained by an appropriate amount of a phosphate buffer. The treatment is continued from 30 min. to 6 hrs. The initial polymer material is colored differently, from yellow to brown, depending on the amount of sulfur introduced. The resulting chromophore system is an indispensable part of the polymer macromolecule, which fact results in a high fastness of the color. Said treatment can be carried out on any conventional periodic-action dyeing equipment adapted for dyeing fibres, yarn or fabric. After the treatment with the sulfur-containing com pound, the solution is drained and the polymeric material is treated for 15 min. with a 3 percent aqueous solution of sulfuric acid. After said period the material is washed with water, wrung and dried.

The semi-continuous method consists of impregnating said polymer or article made therefrom with a concentrated solution of hydrosulfuric'acid or its salts with the pH 7-7.5 maintained by the introduction of an appropriate amount of a phosphate buffer, whereupon excess impregnating solution is removed, the material is steamed, kept in an acidic medium, washed and dried. The impregnation can be carried out on any equipment suitable for the purpose. The removal of excess impregnating solution from the material is effected by wringing or centrifuging. After the removal of excess solution the material is placed into a steaming chamber filled with steam at -l05 C. When dyeing fabrics, use may be made of an air-free ager or sulfuric acid at 20Cduring 15 min.; then the specimen other chamber provided with mea s f r moving th is washed with water and dried with hot air at a tempermaterial in such a manner that the residence time of the ahlre f The ic cq ires n intensi ely goldmaterial in the chamber sh uld la t for 05-450 in en-yellow color with a reddish hue. The color is not repreferably for min. Then the material is subjected to 5 mov from the specimen after extraction with an orother procedures, similar to those employed in the periganic solvent, e.g., ethanol. The content of sulfur in the odi ro s, specimen amounts to 2.5-2.8 wt. percent.

The stability of colors obtained according to the present invention is characterized by the test data for a specimen of fibre made of a copolymer of regenerated l0 EXAMPLE cellulose and polyacrylonitrile, which was colored 5 parts by weight of undelustred viscose fabric congolden-yellow. The data are presented in Table l to foltaining 27 wt. percent of grafted polyacrylonitrile are low. treated with an aqueous solution comprising 3 wt. per

i TXELE i Distilled water Solution of 3 g/l of soap and 5 g/l of Sweat" (30 Friction Light Weather resistance (24 hr) soda (30 min.) min.)

at 40C at 100C I dry wet 5/5/5 515/5 s/s/s 5/5/5 s s 7 s 7 "Th'fasiri 6f 6616;; tested for the effect of wet cent of hydrogen sulfide. The process of treating the treatment and friction has been estimated in accorspecimen is similar to that described in Example 1. The dance with a five-point scale, light fastness and light 25 fabric acquires a golden-yellow color. The content of weather characteristics have been estimated according I sulfur in the specimen is 3.0-3.5 wt. percent.

to an eight-point scale. As can be seen from Table l, the color proves to be very stable to all kinds of action. The color intensity EXAMPLE does not change after 15 hours of ultraviolet irradiation A sample of fabric as in Example 1 is treated with a of the colored specimen by using a mercury-quartz 20 percent aqueous solution of sodium sulfide, with the lamp, the distance between the light source and the pH 7-7.2 and temperature of 70 C, during 5 min. specimen being cm. Said pH value is maintained by introducing monobasic One effect of the present invention consists in that potassium phosphate. After the elapse of said period of the process of dyeing polymers containing nitrile 35 time the fabric is wrung to 100 percent gain in weight groups, and articles made therefrom, becomes essenand Steamed d ing 0 min. Then the Specimen is tially cheaper by obviating the us of vat d c ti i treated with a 3 percent aqueous solution of sulfuricdyes and replacing them by cheap and easily available acid, washed with water, and dried. The content of sulmaterials. fur in the specimen is 4.0-4.5 wt. percent.

Another effect of the present invention consists in the obtaining of colors which prove to be very stable when subject to the action of such external factors as EXAMPLE wet treatment, friction, light, light weather, ultraviolent Polyvinyl alcohol is grafted with 20 Percent of P y irradiation, the polymers and articles made therefrom acrylohitrile y weight of the P y y alcohol) The l acquring a number f new l bl propel-ties resulting copolymer is washed and dried. 5 g of said cof h standpoint f h i future li i polymer are treated with an aqueous solution of sodium Th colors imparted to the polymers or to articles sulfide in the same manner as described in Example 1. made therefrom do not deteriorate after repeated boil- The content of sulfur in the Specimen was ing in solutions of detergents or when subjected to ex- Percent The specimen acquires a golden-yellow Colortraction in organic solvents, such as ethanol, pyridine or chloroform, whereas vat and cationic dyes do become removed from coloredmaterials after being sub- EXAMPLE t jected to extraction in said solvents. 5 Parts by Weight f t y p y of cellu- For a better understanding of the present invention lose polyacrylomh'lle g a on e rayon) by those skilled in the art, given hereinbelow by way of contaml'ng 42 Percent of graft polyhcrylohhfile are illustration are examples'of some particular emboditreated a 10 perfehtcsoluhoh of um Sulfide at a mems f the method f dyeing polynwrstemperature of 73 -75 C for 2-2.5 hours at a pH 7-7.5, maintained by introducing monobasic sodium phosphate, the length of bath being 50. After the treat- EXAMPLE v ment the specimen is removed from the bath and Five parts by weight of undelustred viscose fabric washed with a 3 percent solution of sulfuric acid at containing 27 wt. percent of graft polyacrylonitrile are room temperature for 15 min., then washed with water treated wjth a 5 percent aqueous solution of sodium and dried. The content of sulfur in the obtained specisulfide at a temperature of 75C during 1 hour, with men is 5.2-5.5 wt. percent. The color of the specimen the length of bath being 50 and pH 7-7.5, maintained 65 is orange. The results of testing the color fastness of the by the introduction ofmonobasic potassium phosphate. given specimen when the latter has been subjected to After the treatment the specimen is removed from the the action of various agents are presented in Table 2,

bath and washed with a 3 percent aqueous solution of the values being given in points.

H 6 I TABLE 2 Distilled water Soap and soda Sweat Friction We h at 40C at 100C at 100C wet dry EXAMPLE 6. of bath 50 for 2 hours, then washed with cold water For obtaining saturated orange colors, a specimen of fabric'made of a graft copolymer of cellulose or polyvinyl alcohol and polyacrylonitrile is treated under the conditions described in Example 5 for 5-6 hours with an 8% solution of sodium sulfide in a neutral medium. The content of sulfur is 5.2-6.0 wt. percent.

and dried. The content of copper in the specimen is 1.3-1.5 percent. The specimen is colored khaki with a brown hue. After washing the color deepens. The initial strength of the thread is 200 g/mm after treating with polyacrylonitrile, sodium sulfide and cupric acetate it becomes 210.4 g/mm After keeping the specimen during 192 hours in soil at a depth of 50 cm, the

EXAMPLE 7. J strength of the untreated thread is 24.8 g/mm and that For Obtaining a redbmwn Color, a graft copolymer of the treated thread is 198 g/m n other words, a]. of polyvinyl alcohol and polyacrylonitrile, comprising ost 100 percent preservation of the fibre strength 18 100 percent of graft polyacrylonitrile; is treated in an qbserved- The Qbtamed modified fibres feature a hlgh 8 percent solution of odium sulfide at a temperature llght fastness. Given herembelow are pertinent comparof 70-75 C for 5 hours in a. neutral medium, attained 2O ative data which characterize the tensile strength of the by introducing monobasic sodium or potassium phosthread has been irradiated during hOUl'S phate, the length of bath being 50. After the treatment m y-q p i speclmen ls Wished *1 3 Percent aqueous 9 Resiau'afstr'engtfi' (in percent of the initial value): tron of SUl fUIIC aCICl at room temperature for 15 mm., Untreated fabric I I then washed with water and dried. The content of sul- 2' Fabriotreated with poiyacryionitriie, sodium fur 1S 9.2-9.5 wt. percent. fide and cupric acetate r EXAMPLE 8. v Modified fibresfeature bactericidal properties, the Five parts by weight of mtylonflcomprising -42 pertinent data being presented in'Table 3.

.. TABLE 3, l 7

Tested material Bacterium coli Spigel-la flexneri Staphylococcus Staphylococcus Salmonella Check commune citreus aureus enteridis Untreated viscose fibre Viscose fibre containing nitrite 5 x x x 23 groups (treated with polyacrylonitrile) Viscose fibre containing nitrile 6 x 20 x x r groups, treated with sodium sulfide Viscose fibre containing nitrile 15 12 22 1 24 20 groups, treated with sodium sulfide and cupric acetate The figures indicate the diameter in mm of delay in the growth of bacteria.

+ indicates growth x stands for weakly positive percent ofg'r'ft' polya'crylonitrilefar tieate "Etha 1 0 7 percent solution of sodium sulfide under the conditions v of Example 5. Upon termination of said treatment the fibre is immersed into a 5 percent aqueous solution of cupric acetate at room temperature and with the length The obtained fibre also exhibits hydrophobic properties.

The characteristics of the hydrophobic properties determined by the capillary rise method at multiple launderings are presented in Table 4. i

TABLE 4 Tested material Time of measuring Capillary rise in cm at 20C (min.)

Before laundering After 1st After 2nd After 3rd laundering laundering laundering Untreated fabric 15 7.7 8.5 8.8 9.0 30 9.7 10.2 10.5 10.8 10.6 11.1 11.3 11.7 11.0 11.9 12.0 12.2 Fabric treated with 15 4.2 4.8 5.0 5.2 polyacrylonitrile, 30 6.6 6.7 7.0 7.3 sodium sulfide 45 7.5 7.8 8.7 8.2 I 60 8.5 8.7 9.2 9.6 Fabric treated with 15 0.0 0.5 2.1 3.0 polyacrylonitrile. 30 0.0 1.2 2.3 5.0 sodium sulfide and 45 0.0 1.5 2.4 6.0 cupric acetate 60 0.0 2.0 2.6 6.2

EXAMPLE 9.

Graft copolymer of polyvinyl alcohol and polyacrylonitrile containing 20 wt. percent of graft polyacrylonitrile is kept in an 8 percent aqueous solution of sodium sulfide at 7375 C for 1 hour in a neutral medium at pH 7-7.5, maintained by the introduction of sodium phosphate, the length of bath being 50. After said period of time the specimen is washed with a 3 percent solution of sulfuric acid at room temperature for 15 min., then it is washed with water and immersed in a 5 percent solution of cupric acetate at room temperature and with the length of bath being 50, for 2 hours, with subsequent washing with cold water and drying.

The content of copper in the specimens is 1.0-1.2 wt. percent. The fibre acquires a brown color. The color is fast to the action of ultraviolet radiation. The strength of the fibre after 30 days ofkeepingin soil amounts to 95 percent of the initial value.

EXAMPLE 10.

.-ing min. Then the fabric is treated with 3 percent sulfuric acid, washed with running water and dried. The content of copper in the specimen is 1.5-1.7 wt. percent.

EXAMPLE 11 Five parts by weight ofnitron" fibres (polyacrylonitrile) are treated with an 8 percent solution of sodium sulfide at a temperature of 70'75 C for 4 hours with pH 7-7.5; maintained by introducing monobasic sodium phosphate, the length of bath being 50. The treatment being over, the specimen is removed and washed with a 3 percent solution of sulfuric acid during 15 min., and then with cold water.

The content of sulfur in the obtained specimen is 1.0-1.2 wt. percent. The specimen acquires a yellow color.

What is claimed is:

l. A method of dyeing a polymer containing nitrile groups and selectedfrom the group consisting of polyacrylonitrile, cyanoethylated cellulose, cyanoethylated polyvinyl alcohol, and graft copolymers of polyacrylonitrile with cellulose, polyvinyl alcohol or polyamide polymers in a color ranging from yellow to brown which consists essentially of treating said polymer with a solution consisting essentially of a substantially neutral aqueous solution containing at least 3 percent by weight of a sulfur compoundselected from the group consisting of hydrosulfuric acid, ammonium sulfide and alkali metal sulfides so as to introduce sulfur in the form of sulfhydryl groups into the polymer and then treating the sulfhydrated polymer with a weakly acidic medium having a pH of 4.to 6.

2. A method as claimed in claim 1, wherein the sulfur compound is sodium sulfide.

3. A method as claimed in claim 1, wherein the treatment of the polymer with the aqueous solution of the sulfur compound is carried out in a neutral medium at a pH of 7-7.5 which is maintained by the introduction of a phosphate buffer.

4. A method as claimed in claim 3, wherein the phosphate buffer is monobasic potassium phosphate.

5. A method as claimed in claim 1, wherein the treatment of the polymer with the aqueous solution of the sulfur compound is carried out at a temperature of 60-1 00 C.

6. A method as claimed in claim 5, wherein the tratment with said solutions is effected at a temperature of 80 C.

7. A method as claimed in claim 1 wherein sulfur is introduced into the polymer in an amount not less than 2.5 wt. percent, thereby imparting a yellow to orange color to the polymer.

8. A method as claimed in claim 1 wherein sulfur is introduced into the polymer in an amount not less than 8 wt percent, thereby imparting an orange to brown color to the polymer.

9. A method as claimed in claim 1 wherein the weakly acidic medium is a 3 percent aqueous solution of sulfuric acid.

10. A method of dyeing a polymer containing nitrile groups and selected from the group consisting of polyacrylonitrile, cyanoethylated cellulose, cyanoethylated polyvinyl alcohol, and graft polymers of polyacrylonitrile with cellulose, polyvinyl alcohol or polyamide polymers in a color ranging from yellow to brown which consists essentially of treating said polymer with a solution consisting essentially of a substantiallly neutral aqueous solution containing at least 3 percent by weight of a sulfur compound selected from the group consisting of hydrosulfuric acid, ammonium sulfide and alkali metal sulfides so as to introduce sulfur in the form of sulfhydryl groups into the polymer and then treating the sulfhydrated polymer with a weakly acidic medium having a pH of 4 to 6, followed by treating the dyed polymer with steam at a 7 temperature of -l05 C.

11. A method of dyeing a polymer containing nitrile groups and selected from the group consisting of polyacrylonitrile, cyanoethylated cellulose, cyanoethylated polyvinyl alcohol, and graft copolymers of polyacrylonitrile with cellulose, polyvinyl alcohol or polyamide polymers in a color ranging from yellow to brown which consists essentially of treating said polymer with a solution consisting essentially of asubstantially neutral aqueous solution containing at least 3 percent by weight of a sulfur compound selected from the group consisting of hydrosulfuric acid. ammonium sulfide and alkali metal sulfides so as to introduce sulfur in the form of sulfhydryl groups into the polymer and then treating the sulfhydrated polymer with a weakly acidic medium having a pH of 4 to 6 followed by treating the dyed polymer with an aqueous solution of a salt of a metal selected from the group consisting of copperand nickel.

12. A method as claimed in claim 11, wherein the salt is a salt of bivalent copper.

l 1' I! l 

2. A method as claimed in claim 1, wherein the sulfur compound is sodium sulfide.
 3. A method as claimed in claim 1, wherein the treatment of the polymer with the aqueous solution of the sulfur compound is carried out in a neutral medium at a pH of 7-7.5 which is maintained by the introduction of a phosphate buffer.
 4. A method as claimed in claim 3, wherein the phosphate buffer is monobasic potassium phosphate.
 5. A method as claimed in claim 1, wherein the treatment of the polymer with the aqueous solution of the sulfur compound is carried out at a temperature of 60-100* C.
 6. A method as claimed in claim 5, wherein the tratment with said solutions is effected at a temperature of 70*-80* C.
 7. A method as claimed in claim 1 wherein sulfur is introduced into the polymer in an amount not less than 2.5 wt. percent, thereby imparting a yellow to orange color to the polymer.
 8. A method as claimed in claim 1 wherein sulfur is introduced into the polymer in an amount not less than 8 wt percent, thereby imparting an orange to brown color to the polymer.
 9. A method as claimed in claim 1 wherein the weakly acidic medium is a 3 percent aqueous solution of sulfuric acid.
 10. A method of dyeing a polymer containing nitrile groups and selected from the group consisting of polyacrylonitrile, cyanoethylated cellulose, cyanoethylated polyvinyl alcohol, and graft polymers of polyacrylonitrile with cellulose, polyvinyl alcohol or polyamide polymers in a color ranging from yellow to brown which consists essentially of treating said polymer with a solution consisting essentially of a substantiallly neutral aqueous solution containing at least 3 peRcent by weight of a sulfur compound selected from the group consisting of hydrosulfuric acid, ammonium sulfide and alkali metal sulfides so as to introduce sulfur in the form of sulfhydryl groups into the polymer and then treating the sulfhydrated polymer with a weakly acidic medium having a pH of 4 to 6, followed by treating the dyed polymer with steam at a temperature of 100*-105* C.
 11. A method of dyeing a polymer containing nitrile groups and selected from the group consisting of polyacrylonitrile, cyanoethylated cellulose, cyanoethylated polyvinyl alcohol, and graft copolymers of polyacrylonitrile with cellulose, polyvinyl alcohol or polyamide polymers in a color ranging from yellow to brown which consists essentially of treating said polymer with a solution consisting essentially of a substantially neutral aqueous solution containing at least 3 percent by weight of a sulfur compound selected from the group consisting of hydrosulfuric acid, ammonium sulfide and alkali metal sulfides so as to introduce sulfur in the form of sulfhydryl groups into the polymer and then treating the sulfhydrated polymer with a weakly acidic medium having a pH of 4 to 6 followed by treating the dyed polymer with an aqueous solution of a salt of a metal selected from the group consisting of copper and nickel.
 12. A method as claimed in claim 11, wherein the salt is a salt of bivalent copper. 